The allure of hidden birds

<b>Lori Harvey Contributed Photo</b>Biologist Kim Potter of Rifle untangles a black swift captured in a net as part of a research project. Potter's efforts and findings were recently highlighted in both Audobon and Smithsonian magazines.

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Scientists and bird lovers who study the black swift, a small and mysterious migratory bird that nests behind waterfalls, are known to be obsessive.

Rifle-based biologist Kim Potter, a wildlife technician in the Rifle office of the White River National Forest, is no exception. Potter was the first to document the presence of swifts at Rifle Falls, and has tagged scores of them at Fulton Resurgence Cave in the Flat Top Mountains, north of Rifle. In 2009, she was part of a three-person team that unraveled the longtime mystery of swifts' winter migration patterns.

The team's discovery - that swifts winter 4,000 miles away in the canyons of northwestern Brazil - is highlighted in the current issues of both Audubon and Smithsonian magazines.

Potter said the mystery and uniqueness of black swifts have kept her engaged since she first began to study them in 1996, in her first year as a seasonal technician for the White River National Forest.

"What could be more adventurous and romantic than birds that nest at waterfalls?" she said, laughing. "I can say that I've banded more Black Swifts than anyone in the whole world, and in this day and age, with so many things that are well understood, it's nice to be working on something we know so little about."

To uncover the mystery of swifts' winter migration, Potter and her team fitted eight birds captured in 2009 at the Fulton Resurgence Cave and Box Canyon Falls in Ouray with small tracking devices. The tools, developed by the British Antarctic Survey, log changes in day length, sunrise and sunset to determine latitude and longitude.

The following spring, the team returned to those same nesting sites, recaptured four of the eight birds, and analyzed the data contained in their tracking devices. All suggested the swifts had visited northwestern Brazil.

"As soon as our results were published, we had good publicity across the country," Potter said.

That mainstream recognition has been a long time coming for Potter, who has been a noted authority on Black Swifts within the ornithology community for decades.

Hailing originally from Wisconsin, Potter moved to Rifle from Denver in 1993 and held a series of part-time wildlife positions on the Western Slope before starting in her current job. In the last two decades, she has discovered scores of previously undocumented Black Swift nesting sites throughout the state.

In addition to the mountains and caves north of Rifle, swift nests have also been found throughout the Southwest, in northern California, and as far north as Alaska. Box Canyon Falls in Ouray is a major nesting site, and Potter has journeyed there each spring for several years to observe the birds.

Obsession is a necessary trait in swift researchers, since spotting and tagging the birds often requires scaling remote and slippery waterfalls at dusk, when adult birds are nesting.

"It's somewhat dangerous climbing around the waterfalls where they live," said Jason Beason, special monitoring projects coordinator at the Rocky Mountain Bird Observatory and a member of the migration research team.

Birders are often pushed to such risky behavior by the uniqueness of the Black Swift. In addition to their far-flung migratory patterns, the birds are also distinctive for their tendency to nest much longer than other migratory birds of comparable size, and to lay only a single egg each year.

Many ornithologists believe the birds' predilection for nesting in cool areas around waterfalls could make them vulnerable to the effects of a changing climate. Beason said peak snowfall runoff seems to be occurring progressively earlier in Colorado each year. If waterfalls begin drying up faster each spring, young swifts could be forced to abandon the nest long before they are ready to fend for themselves, he said.

"If the nestlings aren't fully developed and it gets warmer at their nest sites, they may just not make it," Beason said. "But we haven't documented this yet. Right now, it is just a theory."

The next frontier in Black Swift research, Potter said, will be documenting other populations with nesting sites in Idaho and California, and learning whether they, too, spend winters in Brazil.

"If they all migrate to an area, it makes it important to protect that area," Potter said.